ELECTRONIC-PROPERTIES AND VALENCE STATE OF SM IN (SMS)1.19TAS2

We have investigated the valence state of Sm in (SmS)1.19TaS2, which has an alternate stacking of SmS and TaS2 layers, by means of electrical transport, magnetic, and x-ray photoemission spectroscopy (XPS) measurements. The transport properties of (SmS)1.19TaS2 are quite similar to those of other analogs (RS)xTaS2 with a trivalent rare-earth element R, suggesting that the predominant conduction carriers are on the TaS2 layers. On the contrary the magnetic susceptibility is not explained simply in terms of the trivalent Sm with Curie-Weiss behavior. The Sm 3d core-level XPS spectra of (SmS)1.19TaS2 exhibit two sets of peaks associated with both divalent and trivalent Sm initial states, and the portion of Sm2+ is estimated at 0.12. Taking into consideration the conduction mechanism and the charge-transfer rate from SmS to TaS2, it is concluded that the Sm2+-Sm3+ valence fluctuation is realized in (SmS)1.19TaS2. We also propose that carriers are localized on the SmS layer due to the quasiperiodic potential.